After the discovery of the carbon nanotube in 1991, a number of studies have been carried out by many researchers. Various technical improvements and methods of utilization have been discovered concerning carbon nanotubes. For example, nowadays, it is utilized widely for field effect devices, probe top ends for scanning probe microscopes, superconductive materials, highly sensitive microbalances, structural materials, minute forceps for the nanoscale operation, parts for gas detectors, hydrogen energy storage devices, or the like. Moreover, studies have been executed actively for containing the various fillers in the carbon nanotube (Document 1 and Document 2).
For example, as the substances to be contained in the carbon nanotube, a metal such as lead, tin, copper, indium, mercury, an alkali metal such as lithium, sodium, potassium, rubidium, and cesium, a superconductor such as lead, tin, and gallium, a semiconductor such as silicon, germanium, gallium arsenide, zinc selenide, and zinc sulfide, a magnetic material such as samarium, gadolinium, lanthanum, iron, cobalt and nickel, and a mixture thereof have been discussed.
Moreover, an organic molecule semiconductor such as a naphthalene, anthracene, phenanthrene, pyrene, and perylene, an organic dye molecule such as a cyanine dye and a β-carotene, and furthermore, a gas molecule such as hydrogen fluoride, methane, and ethane, or the like have been discussed.
On the other hand, recently, a number of researchers have been involved in the study of the micrometer size area so that the nano thermometer capable of measuring the temperature in the micrometer size environment has been increasingly called for. However, the nano thermometers known so far have a relatively narrow measurable temperature range so that several kinds of the thermometers need to be prepared for each temperature range to be measured in the case of measuring the temperature over a wide range. Due to troublesomeness and high cost, development of a nano thermometer capable of measuring temperature over a wide range by itself has strongly been desired.
Under such circumstances, a nano thermometer utilizing a gallium, capable of accurately measuring the temperature over a relatively wide temperature range has been proposed. As the principle of the temperature measurement, the linear expansion or contraction of the gallium according to the temperature change over a wide range is utilized. By measuring the change of the length of the columnar gallium by a high resolution transmission electron microscopy, the temperature is measured.
The production method for a temperature sensing element comprising a carbon nano tube having a 1 to 10 μm length for containing the columnar gallium and a 40 to 150 nm diameter is known already (Document 3). Moreover, the production method for a temperature sensing element according to the heat treatment at 1,200 to 1,400° C. of gallium oxide powders and carbon powders under inert gas flow has been developed by the present inventors and it is already the subject of a patent application (Application 1).
However, as to the temperature measuring method, utilizing a nano thermometer utilizing a gallium column discussed above, the length of the columnar gallium as the temperature sensing element cannot be read unless the subject to be measured is introduced into the observation area of the high resolution transmission type electron microscope. On the other hand, once the temperature sensing element removed from the inside of the subject to the outside for the temperature measurement, since the length of the columnar gallium returns to the length at room temperature, an accurate temperature of the subject at the high temperature cannot be known.
Document 1: P. Ajayan et al., Nature, vol. 361, page 333, 1993
Document 2: Official gazette of the Japanese Patent Application Laid Open No. 6-227806
Document 3: Gao, Y. H. & Bando Y., Nature, 415,599 (2002)
Application 1: Patent Application No. 2002-67661
Accordingly, an object of the present invention is to solve the above-mentioned problems by providing a novel method capable of accurately measuring the temperature of a subject to be measured at a high temperature even in the case where a columnar gallium temperature sensing element as a nano thermometer utilizing a gallium is removed from the inside of the subject to have the temperature measured at room temperature.